A blog about search, search skills, teaching search, learning how to search, learning how to use Google effectively, learning how to do research. It also covers a good deal of sensemaking and information foraging.

Friday, August 29, 2014

This week was obviously far too easy. Or, the SearchResearch readers have been developing their research skills! I'll assume it was the second. In either case, very nice work. Some people knew the answers off the top of their heads, which goes to show the value of a great social network--you can quickly tap into the collective knowledge base (and superior recognition skills) that your extended personal network has. This isn't to be undervalued! As Howard Rheingold illustrates in his new book, Net Smart, there is a value and a quality of participation that links together bloggers, netizens, tweeters, and other online community participants. This set of people and networks form an online collaborative enterprise that can contribute new knowledge to the world in new ways. And best of all, it forms a personal knowledge network that you can tap into. But we'll talk about that in another post. Today, let's figure out how to search for the answers to these challenges. This week I showed the following three images and asked the obvious question--what are these plants? Here's what I did to answer each question:

1. I found this under a redwood tree in a lawn at one of the Google buildings. I visited here every day for a week, and took this series of pictures over a couple of days. It's shady here, but as you can see, it's just the lawn under the canopy of the redwood. What ARE these things? What's the genus and species name?

A few people reported success with doing Search-by-Image (and that's a great approach). But I did a simple series of searches: [ mushroom dissolving ] Why that query? Because this transformation (from left to right in the images) happened over a short period of time (about 2 days). This was easily the most striking thing about this mushroom. Sure mushrooms often fall apart quickly, but the way the edge of the mushroom just... "dissolved"... was remarkable. So I chose "dissolving" as one of my key search terms. And sure enough, the first hit was to the Mushroom Appreciation site where I learned this is the Coprinus comatus, the "Shaggy Mane" mushroom, aka "Lawyer's Wig" or "ink caps." I then did a search for the binomial name (that is, Coprinus comatus) and found lots of corroborating evidence (and more images that match very closely). As a few other folks did, I discovered MushroomExpert.com (their page on Shaggy Mane) and liked their level of detail in describing how to identify the particular variety. As Mushroom Appreciation writes: "Like a frightened squid or exploding pen, this mushroom releases a black liquid that is laden with spores. As it matures it will deliquesce, meaning it will appear to melt away until only the stem is left." (That word, deliquesce, was new to me, so I did a [ define deliquesce ] -- a lovely term meaning "to become liquid"!) There's also a section on the Mushroom Appreciation site that gives details about how to identify this mushroom (and possibly similar-appearing mushrooms). Apparently this mushroom is also edible, although a bit delicate to prepare. (And you have to move quickly from "just picked" to "just cooked," as they'll deliquesce not long after you pick them. { As always, don't eat any mushrooms until you've taken a class in mycology and identification! It's easy to get really sick or die after eating a mis-identified mushroom. }

2. Here's another thing I found sticking up out of the soil in my garden. This is a particularly well-watered section of the garden--you can see the green beans growing in the background. Just before I took this picture, the brown parts at the tip were covered in flies. I know why, because it smelled terrible--a bit like rotting meat--perfect fly attractant. Unfortunately, I only got one good picture. I took several, but it was in a somewhat difficult to reach place, and this was the only one in good focus. It's about 5 inches long, and seemingly appeared overnight. What IS this thing? (And should I be worried about it?)

For this, the most salient search clues would seem to be: (a) it smells really bad, and (b) it's growing in my garden. I'm going to include "garden" in my search term because I mostly seem mushrooms in lawns, or in woodlands where the places mushrooms grow is fairly stable over time. Since garden soil is churned up at least twice a year, the mushrooms that grow in that kind of place would seem to be very different than "ordinary" mushrooms. So my first query was: [ stinky mushroom garden ] Which gave me the following SERP:

See that row of images? This is called "Universal blended Images" (because the algorithm "blends in" image results into the regular search results. This kind of thing happens only when there's pretty strong evidence that your search terms are all included with the texts describing these images. I was also struck by the appearance of the word "Stinkhorn" on the page several times. What a strange thing! To evaluate this page, I clicked on the row of images to see what was there. It's a surprising set of mushrooms. Such shapes and colors! And all, apparently, stinky. When cruising through the images I found a couple that looked very similar to the picture I took. When I clicked on the first one that seemed very similar, I found myself back on MushroomExpert.com on a page titled "Stinkhorns: The Phallaceae and Clathraceae." There's that word again: Stinkhorn. (And two genus names as well, Phallaceae and Clathraceae.)

I read the MushroomExpert page about Stinkhorns and found an identification key at the bottom of the page. This makes me feel good about the credibility of the content: Good botanical guides will have "keys" like this to help you winnow out the various possibilities. Here's what their key looks like:

From: MushroomExpert.com
Start at step one. Answer the question. If it's true, then you know it's Stahelimyces cinctus.
If that's "Not as above" then jump to question 2. Proceed like this, answering questions
and following the flowchart. If the the "spore slime occurring on the inner surface..." then jump
to question #12.

Sure enough, if you run through their key, you'll find it's a Lysurus mokusin, the "Lantern Stinkhorn." Curiously, for something that smells so bad, it is "... considered to be edible when still in the immature "egg" stage, and is thought to be a delicacy in China. When mature, its foul odor would deter most individuals from attempting consumption..." No kidding.

3. While running through the Stanford Industrial Park (where HP headquarters, Varian, Xerox PARC, and a bunch of Silicon Valley research labs are located) I found the bush below covered in red berries. Each berry is around 1 inch in diameter, and the bushes themselves are used as hedges. It's an attractive plant, and I can see why you'd plant long stretches of this between buildings. Oddly, I've also seen this plant grown as a tree with a trunk planted as a decorative planting along sidewalks. And if I recall correctly, I remember there's some connection with Madrid. What kind of bush/tree is this? And what's the connection with Madrid? What's the genus/species name?

Most SearchResearchers seemed to have ID-ed this by using "Search-by-Image," and that's a fine way to do it. (The trick seems to have been to crop the image down.) But I have to admit to doing the relatively simple description of the most obvious feature: [ strawberry tree ] As luck would have it, the first page of results are all about this tree. I had no idea that it would be THAT easy to identify. As everyone seems to have figured out instantly, this is the Arbutus unedo, aka the "Strawberry Tree," that's commonly planted in temperate climates as a reliable hedge or ornamental. Interestingly, Arbutus unedo was one of the species described by Carl Linnaeus in Volume One of his landmark 1753 work Species Plantarum, giving Arbutus the name it still bears today. This book was the landmark work that set up the whole binomial naming scheme that we still use today. (That is, the Genus species names that we give to organisms.) Given that so many of the names assigned to plants have changed over the past 250 years, it's remarkable that Arbutus unedo still has the same name! Wikipedia entry says: "The fruit is a red berry, 1–2 cm diameter, with a rough surface. The fruit is edible, though many people find it bland and mealy. The name 'unedo' is explained by Pliny the Elder as being derived from unum edo "I eat one," which may seem an apt response to the flavor."Fact checking: For the good of the blog, I ate one of the ripe berries. (After, of course, checking that I had my identification down correctly.) And I can report that they are mealy, with a fairly bland flavor. It was more-or-less a "meh" experience. But unlike a real strawberry, the "mealiness" of the undeo meant that I kept picking little bits of the fruit out of my teeth for hours afterwards. The fruit is really a composite of many tiny bits, so it was a bit like eating a slightly fruity ball of cornmeal. You could eat many of these and survive, but you probably wouldn't want to do so. To make the final connection, I double checked Wikipedia's comment about the undeo fruit appearing on the herald of Madrid. [ Arbutus Madrid ] leads to many confirming pages, including a site that specializes in heraldry, and confirms that the bear is eating the fruit of the Arbutus unedo.

Search lessons

1. Sometime the obvious search is exactly right. I find people often overly complexify their searches. Try the obvious search ( [strawberry tree] or [mushroom dissolving]) and you might well be surprised to see that this is the way many people have written about the topic; meaning that your obvious search will lead to the obvious results. 2. Search by image is great (especially if you use the cropping trick). As a few readers found (cropping the image to get to just the important parts), this works remarkably well. When cropping, choose the parts that you think other photographers will likely focus on. 3. The presence of a identification key marks botanical pages as being serious works. If you've read many plant or flower identification sites, the ones with a "key to identification" tend to be pretty serious sites. Yes, the keys can be intimidating, but it tells me that someone has gone to a LOT of trouble to help us understand how to figure out what kind of plant this is. You don't just toss off a key in a few minutes--they take a lot of time and effort to create. Any site that has one (that they've created) is probably a pretty decent reference source. Next week... a real challenge--a two week challenge (as I'm going on vacation for the first 2 weeks of September)! Get your search skills out, and get ready to research! Search on!

Thursday, August 28, 2014

It's clear that the SearchResearchers don't need much of my help on this week's challenge. You've been zipping along quickly and painlessly. Nice work. I'll write up my method tomorrow, although I doubt any of you will be surprised! If you remember a few episodes ago I wrote about How to search for a special symbol, and gave a link to ShapeCatcher.com as a handy method to find special characters (such as Cherokee "U" -- Ꭴ , or the infinity symbol -- ∞ )You might have noticed that this same capability is now in Google Docs. (See: inserting special characters) When you open a Google document, spreadsheet or presentation, just go to the Insert menuand click Special characters.You'll have multiple ways to find a special character: browse by categoy, search by keyword (example: arrow), enter the Unicode code point (example: 2195) or (best of all)... draw the character.Here's another example from Google Drive's Google+ page (I hadn't thought of searching for an emoticon...)

Another couple of examples--here I draw a contour integral symbol:

Or, something that lots of teachers might want to search for, in this case I search by name:

Wednesday, August 27, 2014

When I go out for a run I usually carry my phone or a camera, just in case I find something odd, peculiar, or spectacular. It's a quick matter to grab the phone and capture the odd plant, animal, street sign, or atmospheric condition that I'd like to understand. Then, when I get back to my computer I can look up the things I've captured and get a bit more of an inside story about where I'm running.

This week I found a few amazing things that I'd like your help in identifying. The Challenge is the same for all three: What IS this? And what can you find out about it?

1. I found this under a redwood tree in a lawn at one of the Google buildings. I visited here every day for a week, and took this series of pictures over a couple of days. It's shady here, but as you can see, it's just the lawn under the canopy of the redwood. What ARE these things? What's the genus and species name?

2. Here's another thing I found sticking up out of the soil in my garden. This is a particularly well-watered section of the garden--you can see the green beans growing in the background. Just before I took this picture, the brown parts at the tip were covered in flies. I know why, because it smelled terrible--a bit like rotting meat--perfect fly attractant. Unfortunately, I only got one good picture. I took several, but it was in a somewhat difficult to reach place, and this was the only one in good focus. It's about 5 inches long, and seemingly appeared overnight. What IS this thing? (And should I be worried about it?)

3. While running through the Stanford Industrial Park (where HP headquarters, Varian, Xerox PARC, and a bunch of Silicon Valley research labs are located) I found the bush below covered in red berries. Each berry is around 1 inch in diameter, and the bushes themselves are used as hedges. It's an attractive plant, and I can see why you'd plant long stretches of this between buildings. Oddly, I've also seen this plant grown as a tree with a trunk planted as a decorative planting along sidewalks. And if I recall correctly, I remember there's some connection with Madrid. What kind of bush/tree is this? And what's the connection with Madrid? What's the genus/species name?

As always, you can click on the picture to see the larger, more detailed version of the image. (And no, there's no useful metadata here in the EXIF of the images.)

If you would, please let us know HOW you figured out the answers. What tools did you use (if any)? What search queries worked for you? And what sidetracks did you take (and then get out of!).

I hope these plants are exotic enough for you. I have to say that I was surprised by each in my searches, and I hope you find this interesting as well.

Monday, August 25, 2014

As you might have noticed by now, I'm not perfect. In fact, I'll wager that all investigative reporters (and the occasional SearchResearch blogger) make mistakes somewhere along the line. It's inevitable.

But an honest writer will try to fix their mistakes--that's what an erratum is all about. In fact, if the web site you're using as a high-quality reference does NOT have a way to update their materials, you might consider that they're not such a great source. Good newspapers, good reporters, good books all have some way to fix the record.

Let me illustrate by example.

Last week a SearchResearch reader, Joel Meltzer, a former resident of the Oneida Community Mansion House in Oneida, wrote to me to point out that:

At some point someone misunderstood the fact that ANOTHER presidential assassin was an Oneida Community member, and drew the mistaken conclusion that Czolgosz was a member. This was then added to the Oneida Community Wikipedia page. (It has since been removed). The statement repeated over and over again, is that Czolgosz was "briefly a member" of the community. No one ever goes into more detail because there is no detail. It just isn't true. Again, he was just a young boy when the community disbanded and he didn't live in Oneida!

Well, that's an interesting claim... and I wondered what could have happened.

Luckily, I have pretty good notes about writing that post, so I went back and reconstructed my searches and zeroed in on what went wrong. Here's my reconstruction:

What went wrong The question for that week was "What's the connection between President McKinley's assassin and "free love"?"

In my post, I showed that Searching inside of the Google News Archives, it was simple enough to find multiple references to Noyes use of the phrase "free love." And then a quick look in Google Books for [ Noyes "free love" ] lead me to Without Sin: The Life and Death of the Oneida Community, Spencer Klaw (1994) where you can find that "in the late summer of 1852, in an article in the Circular [the Colony’s newsletter] he [Noyes] boldly included “Cultivation of Free Love” in a list of principles that the community stood for."

So he's the guy who gave the notion of "Free Love" some currency.

Now, when I looked for a connection to the assassin of President McKinley, I wrote:

"Leon Czolgosz, who shot President McKinley at Pan-American Exposition reception on September 6, 1901. Czolgosz, a native of Michigan and an avowed radical anarchist ( who hung out with people like Emma Goldman) was, for a short time, a member of the Oneida Colony. "

Ever assertion like that needs to come from somewhere, and a good reporter tracks the origin (aka the provenance) of their facts. A great reporter keeps his notes around for years just to be able to revisit questions of fact and inference.

"Charles Guiteau, President Garfield's assassin, was a 5 year Oneida member. Leon Goglsz, for a shorter time, the assassin of President McKinley, was also an Oneida member. (Vowell, 2006)." (emphasis mine)

That's where I got my information. I should have been worried when MacHovec spelled the assassin's name incorrectly (it should be Cgoglsz, not Goglsz). I admit that I did not check the reference to Vowell, 2006, but just assumed that MacHovec represented that information accurately.

Prompted by Joel's question, I pulled out my notes, found the MacHovec citation quickly, and THEN checked (Vowell, 2006), which is by Sarah Vowell (and actually published in 2005 by Simon Schuster). The Google Books link to Vowell's book.

When I downloaded the book (which yes, I had to buy in order to scan completely), I read through every mention of Oneida and every mention of Cgoglsz... and none of them assert that Cgoglsz was a member of Oneida.

So... I assume that MacHovec simply misread the book, or combined notes from different sources together and misplaced Cgoglsz at Oneida.

Since I want to double-source everything, I looked up the Oneida colony history (from multiple sources) and found that they dissolved in 1881 (when Cgoglsz would have been 8 years old). It's pretty clear from the biographies of Cgoglsz that he was working in steel mills from the age of 14, there's just not much possibility that he spent any time at the Oneida Community. (It's also clear from reading a few bios of Cgogslz that he really didn't spend any time at Oneida. Given how much detail these bios have, it's inconceivable that they would have omitted that detail of his life.)

There it is: Leon Frank Czolgosz, born in 1873, assassin of President McKinley, executed by electric chair in 1901, was never a member of the Oneida Community.

On the other hand, Charles Guiteau was, for more than five years, in the Community (he later assassinated President James Garfield), so there is still a story line connecting the ideas. Note that there's no causal relationship here (free love doesn't lead to becoming an assasin), but there is an interesting accident of history that these stories should cross.

I'll go edit the original post to link to this. Erratum duty discharged.

Friday, August 22, 2014

Oh yeah... I forgot the historical connection. Hannibal. Elephants. 218 BC. 25,000 soldiers marching from Barca to Roma. If you do any searches with Alps, mountain passes, Oulx (etc) you'll find that the southern route is one of those that's proposed as the way Hannibal got his elephants from Spain to Italy. It's a heck of a walk for an army, especially one that's got 37 elephants. (That's the number he ended up with. We don't know how many he started with.) And while historians debate exactly which mountain pass they hiked through (with elephants!), it had to be one of these routes. (Another version of the march from Barcelona to Rome.) All the other passes are worse!

I asked two simple routing questions that takes a bit of figuring to get an answer: In both cases, there are two obvious routes from Point A to Point B. The question is simple: Which route is flatter? (To be precise, find a route with the smallest elevation gain.)

1. Suppose I'm in the Southwest of the US and want to do a bike ride from Farmington, New Mexico, to Durango, Colorado. What route would you recommend for the least overall elevation gain between the two cities?

2. Suppose that a few months later I'm in the Southeast of France and want to ride my bike from Echirolles (France) to Oulx (Italy). What route would you recommend for the least elevation gain between these two cities?

As several sharp-eyed readers pointed out, Google Maps just recently announced a bike route elevation tool to help answer exactly this question. (Google's announcement; TechCrunch; ...) You can compute bicycle elevation profiles (currently) in all the 14 countries Google offers biking directions. (Austria, Australia, Belgium, Canada, Switzerland, Germany, Denmark, Finland, Great Britain, Netherlands, Norway, New Zealand, Sweden, US) Unfortunately, France and Italy aren't included... So to solve the first Challenge, the easiest thing to do is just use Google Maps, use "Find Directions" and then select the Bicycle Route option. Here I've just asked for the bike route from Farmington, NM to Durango, CO. It's a lovely ride, almost 52 miles long, with an elevation gain of 1,588 feet.

There's another obvious route that would leave Farmington on 170/140/160 to Durango. To see the elevation profile for that route, I just drag the route from where it is (by pressing-and-holding on one of the small circular "control points" on the line) to where I'd like it to go:

Once I've moved it to Route 170, the map looks like this:

This route, by contrast, is a bit shorter but has a bit more climbing in it (2,444 ft vs. 1,588 ft).

But as Ramón pointed out in his link to the "Climb = what flat distance" article, there are often many factors to take into account when computing route relative difficulty. This is a fascinating discussion, but since I want to ride this route anyway, I'm just going to pick the route that has the least elevation gain. (Side note: That article is written by cyclists in Florida, one of the world's flattest states, where, I suppose, they worry about things like this!)

It's important to recognize that there ARE multiple tools to figure out this kind of information, each with its own capabilities. In the Strava app you can sweep your mouse over the elevation profile at the bottom and read off the elevation and grade. As you move the mouse, the blue dot follows along on the map just above it. (This is true for Google Maps as well--move the mouse along the profile and see where the dot is on the route. But Maps doesn't show the elevation or grade at that location.)

Answer to route 1: I'm going to stick with the first route (550/160). It's a little less climbing. And spot-checking the Streetviews along the route suggests that the road has nice shoulders, not a lot of traffic, and nice views.

Question 2: Echirolles (France) to Oulx (Italy) We already know that Google Bicycle Routes won't work there? What to do?

Answer: Find another tool to do the same kind of work. I liked Ramón's query to find such tools

[ cycling routes elevation comparison ]

this set of results leads to many tools for doing this kind of analysis. For my profiling, I happened to use Veloroutes.org (but others work as well). Here's the profile for the obvious southern route from Echirolles to Oulx:

AND... If you click on the "get elevation image" (upper right of the blue box), you'll see just the elevation of the route selected.

And I note that this route is 123.6 km long, with 3262 m gain, with a max grade of 30%. (That's a HUGE grade! And there are two big hills.)

Here, for contrast, is Rosemary's Strava map of the same route:

Interestingly, this map shows a max grade of 17.1% (which is much less than the 30% I saw on my map). Since neither mapping service tells how they measure grade, it's hard to know which is more accurate--but all cases, this is a steep route.

When I did the same plot for the other (northern route), I get this map:

This route is 155.3 km, with 2837 m gain, with a max grade of 20%. (That's still a big grade, but much better than 30%.)

Here's the elevation profile for the northern route.

Ramón also found a different bike route elevation site (PerfildeRuta) that does very much the same thing (also available in English). Here's their diagram of this route. Note that they believe the maximum grade on this route is 47%! (Really? That's not a grade--those are stairs!)

And if I now spot check the two routes, the southern route looks MUCH more appealing. The northern route is mostly major highway, while most of the southern route looks like this...

BUT the Southern route is very appealing. And as Rosemary points out, it goes right next to the Alp d'Huez, one of bicycling's most revered roads for its dramatic races throughout the history of the Tour de France.

If I was to do this ride, I'd definitely go the Southern route. Longer, steeper, but MUCH more appealing.

Search Lessons(1) Always keep up-to-date on announcement about new search capabilities. While people have always created elevation profiles, it's much easier if you know about the tool that does exactly that. (2) When using a new UI (such as that in the VeloRoute elevation profiler), pay attention to options that might not be well-marked.The "get elevation image" is exactly what I wanted from this map, but it's a pretty hidden function. (3) Keep tracking of an evolving question. Even when the person asking the question says "I want the flatter route," the process of learning about the question often reveals information that overrides the initial criteria. This kind of thing happens all the time in real research questions. You start with question A, but in the process of research you discover additional information that changes the question into B, then maybe question C... This is the nature of research, and definitely of search. Which is why we do SearchResearch; it's a fascinating way to learn more about the world at large. And now I need to go for a bike ride. Thanks to everyone who wrote it on the comments. Keep 'em coming. Search on!

Wednesday, August 20, 2014

AS you've probably figured out by now, I love to go for long bike rides, especially in hilly terrain. Mountains? Bring 'em on. Rolling hills? Even better. But that doesn't mean I don't pay attention to the hills. Every cyclist wants to have some idea about what's coming up, if only to be sure to have brought along enough water and food. A common thing for cyclists to do is to check the routes before heading out, just to see how hilly the day looks to be. Or, more commonly, to choose a route that matches your abilities (and aspirations) for the day. Some days, you want to attack the hills--other days, you need to rest a bit. That common question leads to two fairly simple route selection Challenges. In both cases, there are two obvious routes from Point A to Point B. The question is simple: Which route is flatter? (To be precise, find a route with the smallest elevation gain.)

1. Suppose I'm in the Southwest of the US and want to do a bike ride from Farmington, New Mexico, to Durango, Colorado. What route would you recommend for the least overall elevation gain between the two cities?

2. Suppose that a few months later I'm in the Southeast of France and want to ride my bike from Echirolles (France) to Oulx (Italy). What route would you recommend for the least elevation gain between these two cities?

The routes here are pretty obvious--when giving your answer, just say which roads you recommend. (For example, in NM/CO, do you recommend routes 140 and 170, or 550? I don't need turn-by-turn routes, unless you find a REALLY unusual solution.) I'll give a hint tomorrow about how I solved these Challenges, but for today, I'll let you work on them. (And we'll chat about why there are two versions of the same problem.) As usual, in addition to your solution, be sure to tell us your thinking--HOW did you solve the Challenge? And what deadends did you explore along the way?

For an unusual extra credit (and really optional): Why is the route from (somewhere near) Echirolles to (somewhere near) Oulx of historical interest? Who else would have deeply cared about finding the flattest path between these two locations?

Friday, August 15, 2014

First off, excellent work by all. I'm not sure I have a lot left to add to the discussion. You're a crack SearchResearch team! But let's look at some of the ways people investigated our Challenge this week. Remember that I asked: 1. Can you find the GPS coordinates of the manhole cover shown below? And why does it have that odd shape? (Neither triangular nor circular...)

When I posed this question, I didn't dream that you'd actually be able to find THIS PARTICULAR cover, which is why I added "...you don't have to find exactly this instance of a manhole cover, but just the coordinates of any manhole cover that has this particular shape."But I didn't actually do the Search-By-Image to test that before posting. In a great feat of sleuthing, Passager, AlmadenMike and Pete Warden both found that the original image was by Owen Byrne. That's great. Nice work. Then Pete went on to contact Owen Byrne on Twitter (@owenbyrne) where he confirmed that this particular photo was his. Oh, and by the way, Owen's reading of the comments thread helped him remember that the original photo was taken at "4th and China Basin in Mission Bay." With that hint, it's simple to use StreetView to fly over to the intersection of "4th and China Basin" in San Francisco and find the following. (I added the red circles to highlight the covers embedded in the street.)

A quick Command-click (or right-click for PC users) on the intersection tells me that this is 37.772019, -122.389509. None of these have a red stripe, but the color could have well worn-off (or was not yet applied) when the StreetView car drove by. Nearly everyone else did some version of an initial search for: [San Francisco reclaimed water covers]

and quickly learned that these particular covers are "Valve covers used in the Mission Bay Project of San Francisco to differentiate reclaimed water from potable water are in the shape of a Reuleaux triangle."When you check out the meaning of Reuleaux triangle, you find the Wikipedia page which tells us that "It is a curve of constant width, meaning that the separation of two parallel lines tangent to the curve is independent of their orientation. Because all diameters are the same, the Reuleaux triangle is one answer to the question "Other than a circle, what shape can a manhole cover be made so that it cannot fall down through the hole?" And, like many other people, I found this fascinating, and thought how clever these folks were to design their valve covers in this way. But then I followed my search principle of "Use whatever information you have." which included the name of the foundry that cast the cover. (Look at the original image: it says "D&L Fdry" on it.) So I did a search for that: [ D & L Fdry ]which led me to the foundry's web site... and their catalog! It didn't take much looking before I found the catalog entry for the "Reuleaux triangle" valve. Here's the diagram from their catalog:

And so while it's true that a Reuleaux triangle cannot fall through the hole it inscribes, this particular design doesn't take any advantage of that fact. The hole is so small that there's no way the cover would fall through. (In any case, the Reuleaux triangle shape is for the outside of the valve cover, and not the shape of the cover itself.) The bottom line is that this clever shape is used solely as a unique visual shape, and not for its physical properties. It might just as well have been just a triangle. Ah, well. It's a great story, just not the story you might have thought. Excellent job by all. Special kudos go to Pete for tracking down the original photographer and asking him where it was!

And now...the other sewer covers....
I hadn't really planned on doing searches for these covers, especially since I know where they are!

This one is near my office at the GooglePlex in Mountain View, CA.I like the pattern, even though it's a common one. Turns out lots ofservice covers in the area are tagged with the name of the companythat owns the service box (in this case I think it's fiber optics).

This was kind of a no-brainer. That's Mickey in the middle.Taken from Disneyland in Anaheim, CA.

This one isn't hard to figure either. The text is Italian,and anything that's tagged with SPQR has gotto be in Rome. (Look it up.) This is a cover for afirefighting hydrant in Rome. See Wiki for more.

As Rosemary pointed out, the name of this image file is "Cover-Tokyo.png"That's a big clue right there. This was from one of my trips to Japan,where they really DO have the most beautiful sewer coversin the entire world. See this remarkable collection of Japanese sewer covers (and thanks to Ramon for finding the collection).

Search lessons:A lesson for me--always do a Search-By-Image to see if the image you're using actually appears somewhere else! As most searchers discovered, it wasn't too hard to go from description to the key idea (the "Reuleaux" triangle) that led to identifications. But as I point out, just because something has a unique geometric property ("constant width curve"), you should NOT assume that it actually makes use of that property in a meaningful way. I have to admit to being surprised when I saw the D&L Foundry catalog. And finally... I'm glad that several readers commented about "never looking at manhole covers again in the same way..." That's one of the beautiful things about getting the chance to write this blog--I see almost everything in a slightly different way these days. I know I can find out the most remarkable things about the world. With just a little research inclination and a few skills, the world is ready to tell you amazing stories, if only we learn to pay attention. Excellent work by all. Nicely done.